Protein Immunoglobulin heavy chain variable domain, VH [88543] (22 species)VH domains of human and mouse antibodies are clustered by the sequence similarity within the germline encoded segment and then by the size of the complementarity determining regions CDR1 and CDR2, so the clusters may correspond to putative germline families in the species genomes; VH domains with artificial or grafted exogenous CDRs are listed as engineered species